Christavia MK-1

Time for a Christavia update. Becky blogged "It All Started With An Engine" on March 15, 2009. Lot's has happened since then. The first thing we did was order Spruce wood from a local aircraft restoration business in Scappoose. Once received, we went to work on building a jig to turn out identical ribs for the wings. I'll report more completely on that process later. The ribs are completed, but attaching them to the spars is yet to come.

A project such as this needs one really long table. Scrounging up what we had and adding to it a table given to us by some hangar friends, we were up and running. The table is roughly 17 feet long.




Aircraft Spruce in Southern California deals in just about everything you need to build an airplane. After a LOT of research, they were also the best deal in purchasing the steel for the tubular fuselage. The 4130 steel is more commonly known as Chromoly and is used where strength and light weight are important. It is used in high performance bikes, dune buggies, and other race machines. The 24 foot lengths showed up on a huge truck, loaded in a long cardboard tube, along with the aluminum sheeting we need for the leading edges to the wings and some areas of the body of the plane.

We asked a few local builders for some Chromoly scrap. Becky went to work practicing her welding with a couple different TIG (Tungsten Inert Gas) machines as well as using her OxyAcetylene system.






















The first piece cut was the longerons. These are the longitudinal pipes that the other pipes are fit up against. The pipes are laid out and a line is drawn down the length of the tube, marking the center.
Measurements are taken and the appropriate lengths are cut. After cutting, some needed to be bent in a few spots. This was done by using the torch to heat the area red-hot and applying mild pressure to get the shape we wanted.





After we drew the picture of the fuselage on the table, we measured exactly how long each pipe needed to be. She ran these measurements through a program that told her how long to cut each pipe and exactly where and at what angle to notch the ends so that there was as little gap between the fitted pipes as possible. Each cut was fine tuned with a bench grinder.







Once assembled on the table, the ends of each piece were cleaned and a #40 hole was drilled on the mated pipe. Now comes the fun part. After trying a couple different TIG welders, we decided she needed one to call her own. The new machine with it's newer technology proved to be a good move. She laid down small tack welds - just enough to hold the pieces of Chromoly all together until the next step. After the left side of the fuselage was completed, we started placing the pieces for the right side into the jig. When it's done, both sides will be mated and it'll start to look like an airplane!

This is a bit to grasp, but once the entire welding process is done, we are going to run Boiled Linseed Oil into the inside of every tube, then drain it out. These little holes allow the oil to run throughout the framework, coating the inside to prevent breakdown over the decades.